1. Field of the Invention
The present invention relates to a portable apparatus and a portable timepiece equipped with a pushbutton switch.
2. Description of the Related Art
Some portable apparatuses such as a portable timepiece, for example, a wristwatch or a pocket watch, a stopwatch, a mobile phone, and a personal digital assistant have, mounted on the apparatus exterior body, a pushbutton for operating, for example, a contact in the apparatus exterior body. In the case, for example, of a portable timepiece, by pushing in the pushbutton by a predetermined stroke, it is possible to switch the illumination of the dial or the timepiece display from analog to digital display or vice versa, or to correct the date or the day of the week digital-displayed.
In a portable apparatus of this type, the pushbutton is urged by a spring in a direction reverse to the pushing-in direction thereof, so that detachment of the pushbutton from a pipe due to this spring force is prevented. For this purpose, a C-type or E-type retaining ring configured to be get caught by an end of the pipe is provided at an end portion of the pushbutton reaching the interior of the apparatus exterior body through the pipe fixed to the apparatus exterior body.
In view of this construction, the conventional portable apparatus is equipped with a lock member for preventing erroneous operation of the pushbutton. The lock member has a female screw portion formed in the inner periphery thereof, which is threadedly engaged with a male screw portion formed on the outer periphery of the pipe fixed to the apparatus exterior body, and is provided so as to be movable between a lock position and a non-lock position through a change in the mesh-engagement between these screw portions (See, for example, JP-A-2003-7164 (Patent Literature 1)).
In this construction, when the lock member is moved to the non-lock position, the lock member is detached from the head of the pushbutton having passed through the pipe. Thus, the pushing-in operation of the pushbutton is allowed by a stroke corresponding to the detachment distance. Conversely, when the lock member is moved to the lock position, the lock member is brought into contact with the head of the pushbutton. As a result, the pushing-in of the pushbutton is prevented.
In the prior-art technique, the retaining ring mounted to the pushbutton is caught by an end of the pipe inside the apparatus exterior body, whereby the pushbutton is set in position; and the lock member moved to the lock position is brought into contact with the head of the pushbutton in this state. Thus, even in the state in which the pushbutton is locked, the mesh-engagement state between the male screw portion and the female screw portion is maintained.
Substantially to the reaching of the lock position by the lock member, it may occur that the lock member having the female screw portion or a rotary ring is erroneously rotated to an excessive degree by the operator.
Such an erroneous operation is possible for the following reason. That is, the strength of the retaining ring is not so great, and the elastic deformation of the retaining ring is relatively easy; further, the retaining ring has a notch, so that it is capable of deformation so as to be reduced in diameter. Thus, due to the elastic deformation of the retaining ring, it is rather difficult for the user to sense that the lock member has reached the lock position. Owing to this, it can happen that the lock member or the rotary ring is erroneously operated as described above.
When the lock member or the rotary ring is erroneously rotated to an excessive degree, it can happen, as a result thereof, that the deformed retaining ring is drawn into the pipe. As a result, there is a fear of a smooth axial movement of the pushbutton after the erroneous operation being hindered. In particular, when, in order to improve operability, the lock member or the rotary ring is designed in a larger diameter, the rotational torque due to the erroneous operation mentioned above is augmented. As a result, the retaining ring becomes easier to deform, and there is high possibility of the retaining ring being drawn into the pipe. Furthermore, the problem due to the above-mentioned erroneous operation constitutes a hindrance factor to designing the lock member or the rotary ring in a larger outer diameter.
It might be possible to cope with the above-mentioned problem by increasing the wall thickness of the retaining ring or forming the retaining ring of a high-strength material so as to make it harder for the retaining ring to undergo deformation. This, however, requires a dedicated retaining ring to be newly developed, resulting in an increase in cost. In addition, the operation of attachment/detachment of the retaining ring to/from the shaft portion of the pushbutton is a bother, resulting in great deterioration in workability when the components around the pushbutton are dismantled for cleaning. Thus, the above measure is not desirable.
And, in avoiding generation of a problem due to the above erroneous operation, it is desirable to suppress an increase in cost. For this purpose, it is desirable to avoid an increase in the number of components as far as possible, and to make the component structure as simple as possible. When these conditions are satisfied, the assembly and the component machining are facilitated, and it is possible to suppress an increase in cost.